1. Field of the Invention
The present invention relates generally to molten metal pouring amount control apparatus which is attached to a bottom of a molten metal container such as a ladle and tongue dish and slides a sliding plate to adjust an opening of a nozzle hole between the sliding plate and a fixed plate so as to control a molten metal pouring amount.
2. Description of the Related Art
Usually, the molten metal pouring amount control apparatus comprises a fixed plate made of refractory product detachably attached to a base plate fixed on a ladle or the like having a nozzle hole and a sliding plate made of refractory product detachably attached to a slide frame having a nozzle hole. By sliding the slide frame along the base plate, openings of a nozzle hole of the fixed plate and that of the sliding plate are adjusted so as to control a pouring amount of molten metal.
The sliding type of the slide frame in such a molten metal pouring amount control apparatus includes metal sliding type and roller sliding type.
Examples of the metal sliding type have been disclosed in Japanese Patent Application Publication No. 48-4697, Japanese Patent Application Publication No. 7-75771 and Japanese Patent Application Laid-Open No. 7-164134.
According to this metal sliding type, a sliding face between the fixed plate and sliding plate and a sliding face between the slide frame and guide member are coated with lubricant so that the sliding plate is pressed against the fixed plate through the slide frame so as to prevent a leakage of molten metal. To slide the slide frame to adjust the opening of the nozzle hole, a driving force larger than a sum of a frictional force generated on the sliding face between the fixed plate and sliding plate and a frictional force generated in the sliding face between the slide frame and guide member is necessary.
In this case, because the frictional force generated between the slide frame made of metal material and guide member is large, a high-output driving means (usually, a hydraulic cylinder is used) is necessary for driving the slide frame and a strength sufficiently capable of bearing a high load is needed.
Further, because the slide frame and its guide members are worn out, they need to be replaced with new one before or after 500 heats for example. Thus, maintenance cost such as disassembly cost and parts cost increases. Further each time when molten metal is charged, the sliding face between the fixed plate and sliding plate and the sliding face between the slide frame and guide member must be coated with lubricant, and this work is troublesome.
However, according to the metal sliding type, a spring force application point always exists below the nozzle hole of the fixed plate and nozzle hole of the sliding plate even if the slide frame is slid. Therefore, there is an advantage that a pressing force around the nozzle hole which is the most important is secured and this is why the metal sliding type has been widely used up to now.
The other type of roller sliding was invented to solve a problem on friction generated in the aforementioned metal sliding type and has been disclosed in, for example, Japanese Patent Publication No.SHO62-58816 and Japanese Patent Publication No.HEI1-38592.
According to the former invention, as shown schematically in FIG. 12, rollers 107a, 107b are provided at fixed positions on a guide member 106 and a slide frame 105 having the sliding plate 103 is installed on these rollers 107a, 107b. Then, the sliding plate 103 is pressed against a fixed plate 101 by a spring 108 interposed between a casing cover 109 and a guide member 106 (hereinafter this is referred to as a fixed roller type) According to the latter invention, as shown schematically in FIG. 13, the rollers 107a, 107b are provided on the slide frame 105 and then, mounted on the guide member (rail). The sliding plate 103 is pressed against to the fixed plate 101 by the spring 108 (hereinafter this is referred to as moving roller type).
Such a roller sliding type is capable of reducing a frictional force generated in sliding of the sliding plate by using the rollers and reduction of its unit price and maintenance cost can be expected.
In the fixed roller type of the aforementioned roller sliding type, when the nozzle holes 102, 104 are fully opened, as shown in FIG. 12(a), the pressing force of the sliding plate 103 is applied around the nozzle hole 102 of the fixed plate 101 by the rollers 107a, 107b uniformly, so that portions around the nozzle holes 102, 104 make firm contact with each other. Thus, there is no fear that any molten metal invades in between the fixed plate 101 and sliding plate 103.
However, because the positions of the rollers 107a, 107b are constant, as the slide frame 105 is moved in a direction for closing the nozzle holes 102, 104 (direction indicated by an arrow), as shown in FIG. 12(b), acting points of the rollers 107a, 107b against a portion around the nozzle hole 104 of the sliding plate 103 are moved, so that the pressing force applied around the nozzle hole 104 becomes unstable. Further, when the nozzle holes 102, 104 are closed fully, as shown in FIG. 12(c), the nozzle hole 104 is apart from the acting points of the rollers 107a, 107b, so that the pressing force around the nozzle hole 104 drops.
In this condition, molten metal is likely to invade in between the fixed plate 101 and the sliding plate 103 through the nozzle hole 102. If the invading molten metal is solidified, the contact of the sliding plate 103 by pressing with the springs 108 becomes difficult, so that a leakage of the molten metal is generated from a gap between the both plates.
On the other hand, in case of the moving roller type, although the pressing force around the nozzle hole 104 in the sliding plate 103 is stabilized different from the case of the fixed roller type, as shown in FIG. 13(a), the pressing force around the nozzle hole 102 in the fixed plate 101 drops as the slide frame 105 is moved in a closing direction (direction indicated by an arrow) as shown in FIGS. 13(b), (c). Therefore, the same problem as the case of the fixed roller type is generated.
In such a fixed roller type and moving roller type, if a distance between the rollers 107a and 107b is made long, the pressing force around the nozzle holes 102, 104 can be secured in an entire range from the full opening of the nozzle holes 102, 104 to the full closing thereof. In this case, naturally, the slide frame 105, guide member 106 and casing cover 109 have to be extended. Consequently, the entire apparatus becomes very long, so that not only increase of cost is induced, but also this apparatus may not be mounted on a bottom face of the molten metal container.
Further, because the rollers 107a, 107b have to be reduced in size, the service life of shafts for supporting them is short and therefore they have to be replaced sometimes. Thus, maintenance cost cannot be saved sufficiently. Further, because complicated parts such as a lever and the like in the invention described in the aforementioned Japanese Patent Publication No.SHO62-58816 and an intermittent rail and the like in the invention described in Japanese Patent Publication No.HEI1-38592 are necessary, reduction of the price of the apparatus cannot be expected.
For the reason, although the molten metal pouring amount control apparatus based on the roller sliding type has a technical advantage that the sliding friction of the slide frame is small, it cannot currently be in a mainstream of sliding type of the slide frame.
Accordingly, a first object of the present invention is to solve the above described problems and provide a molten metal pouring amount control apparatus in which the sliding resistance of the slide frame is small and the pressing force around the nozzle hole is stabilized so that there is no fear that any trouble such as a leakage of molten metal occurs and a structure thereof is simple and production cost and maintenance cost are cheap.
On the other hand, a conventional sliding plate for use in the above described pouring amount control apparatus is shown. A first example is a polygon plate whose plain view and side sectional view are shown in FIG. 18 and FIG. 19 respectively. A second example is an oval plate 113 whose plain view and side sectional view are shown in FIGS. 20, 21 respectively. Reference numerals 112, 114 denote nozzle holes of the respective plates. Upon use, these plates are overlaid and one of them is slid as a sliding plate so as to control opening/closing of the nozzle hole to adjust the flow rate of molten metal.
From previous operation experience for a long time, most molten metal leakage occur when the nozzle is located at the opening position and it hardly occurs at the closing position thereof. The reason is that although a function for controlling a passage amount of the molten metal is necessary at the opening position of the nozzle, a function necessary for the closing position is only to stop the flow of the molten metal.
However, conventionally, the shape at the opening position or closing position of the nozzle hole has not been determined sufficiently reasonably considering its function and economic performance.
The sliding plate is melted and lost by a passage of high temperature molten metal and the like. Therefore, there is a fear that the molten metal and the like may leak if it is used too frequently. Thus, the sliding plate is replaced every several charges and handled as a consumption product However, because this sliding plate is made of refractory product like an expensive brick, the running cost is high and this is an obstructive factor against reduction of cost.
Therefore, a second object of the present invention is to form a sliding plate in an economic shape within a range which does not generate a leakage of the molten metal in views of these problems so as to reduce the unit price thereby achieving a reduction of long period cost to a large extent.
(1) To achieve the above described object, according to a first aspect of the present invention, there is provided a molten metal pouring amount control apparatus comprising: a driving means for a slide frame; a base plate which is provided with a fixed plate having a nozzle hole and is to be attached to a molten metal container; a frame which is mounted to the base plate through a hinge in such a manner that the frame can be opened and closed; and a slide frame which is accommodated in the frame slidably in a horizontal direction, driven by a driving means and provided with a sliding plate having a nozzle hole, and in which the sliding plate is pressed against the fixed plate by springs interposed between the sliding plate and the frame, the molten metal pouring amount control apparatus further comprising guide units each having a plurality of steel balls disposed in line between the slide frame and the springs, the guide units being disposed on both sides of the sliding plate.
With this structure, the sliding resistance of the slide frame is small and the driving means can be reduced in size. Further, the pressing force around the nozzle hole is stabilized so that there is no fear that a leakage of molten metal occurs and the structure is simple and therefore maintenance cost can be reduced.
(2) According to a second aspect of the present invention, there is provided a molten metal pouring amount control apparatus according to the first aspect wherein each of the guide units includes: a retainer having a plurality of holes arranged in line so that the steel balls are accommodated rotatably in the holes with upper and lower portions of the balls being exposed through the holes; an upper lace which is provided with a guide groove on its bottom face and fixed on a bottom face of the slide frame; and a lower lace which is provided with a guide groove provided on its top face and fixed on a spring receiver disposed on a plurality of the springs movably up and down between a guide frame and the frame, the retainer being nipped between the upper and lower laces.
As a result, such an event that adjacent steel balls contact each other thereby obstructing a rotation thereof never occurs, so that the slide frame can be slid smoothly. Further, the pressing force of the sliding plate by the spring can be stabilized regardless of the position of the slide frame.
(3) According to a third aspect of the present invention, there is provided a molten metal pouring amount control apparatus according to the second aspect wherein each of gaps between the retainer and the upper lace/the lower lace is 0.1-1.0 mm.
As a result, the sliding resistance can be reduced and there is no fear that foreign matter invades in between the steel balls to resultantly increase the sliding resistance or damage the steel balls and retainer.
(4) According to a fourth aspect of the present invention, there is provided a sliding plate having a nozzle hole for use in a molten metal pouring amount control apparatus, for controlling a pouring amount of molten metal, wherein assuming a center position of the nozzle hole is X, a diameter of the nozzle hole is a, a distance from an edge of the nozzle hole up to the nearest edge of the plate is d1, a position apart from the center position X of the nozzle hole by a distance S (=2a+xcex2) is Y, and a distance from a virtual circle of the diameter a around the position Y up to the nearest edge of the plate is d2,
a pad ratio xcex11=d1/a is set in the range between 0.8 and 1.5,
a pad ratio xcex12=d2/a is set in the range between 0.4 and xcex11 and safety distance xcex2 is set in the range of 0-60 mm.
With this structure, the sliding plate can be formed in an economic shape within a range in which no leakage of molten metal occurs.
(5) According to a fifth aspect of the present invention, there is provided a sliding plate wherein an external shape of the sliding plate is polygon so as to make it easy to fix the plate.
(6) According to a sixth aspect of the present invention, there is provided a sliding plate wherein part of the external shape of the plate comprises part of a first polygon having a virtual inscribed circle of a diameter (a+2d1) around a position X and part of a second polygon having a virtual inscribed circle of a diameter (a+2d2) around a position Y.
(7) According to a seventh aspect of the present invention, there is provided a sliding plate wherein d2=d1/2.
Consequently, not only the sliding plate can be formed in an economic shape within a range in which no leakage of the molten metal occurs, but also the plate can be fixed more easily by using straight sides of the polygonal shape.
(8) According to an eighth aspect of the present invention, there is provided a sliding plate wherein respective corners of the polygonal shape are replaced with arcs.
Consequently, the size of the sliding plate can be further reduced economically.
(9) According to a ninth aspect of the present invention, there is provided a sliding plate wherein the thickness of a portion around the nozzle hole is larger than the thickness of the other portions.
Consequently, because a thicker portion than the other portion exists around the nozzle hole, the upper and lower nozzles can be engaged with each other easily.